Pressure atomizing burners or liquid spray heads have been heretofore used to atomize liquid in the various fields of art as mentioned above. The term "liquid" herein used is intended to mean not only liquid but also various liquid materials such as solution, suspension and the like. Injection nozzles used on such spray burners and liquid atomizers are adapted to atomize the liquid by virtue of the shearing action between the liquid discharged through the nozzles and the ambient air (atmospheric air). Accordingly, increased pressure under which the liquid was supplied was required to achieve atomization of the liquid, resulting in requiring complicated and large-sized liquid supplying facility such as pumps, piping and the like.
Furthermore, regulation of the flow rate of injection was effected by varying either the pressure under which to deliver supply liquid or the area of the nozzle outlet opening. However, the former method provided poor liquid atomization at a low flow rate (under a low pressure), as a remedy for which air or steam was additionally used on medium or large-sized boilers to aid in atomization of liquid, requiring more and more complicated and enlarged apparatus. On the other hand, the latter method required an extremely intricate construction of nozzle which was troublesome to control and maintain.
In order to overcome the drawbacks to such prior art injection nozzles, attempts have been made to impart ultrasonic waves to liquid material as it is injected out through the jet of the injection nozzle under pressure.
However, the conventional ultrasonic liquid injecting nozzle had so small capacity for spraying that it was unsuitable for use as such injection nozzle as described above which required a large amount of atomized liquid.
As a result of extensive researches and experiments conducted on the ultrasonic liquid atomizing mechanism and the configuration of the ultrasonic vibrating element in an attempt to accomplish atomization of a large amount of liquid, the present inventors have discovered that it is possible to atomize a large quantity of liquid by providing an ultrasonic vibrating element formed at its end with an edged portion along which liquid may be delivered in a film form, and have proposed an ultrasonic injection nozzle based on said concept as disclosed in Japanese Patent Application No. 59-77572.
The present inventors have discovered through further studies and experiments on the configuration of the vibrating element for such ultrasonic injection nozzle that the configuration of the vibrating element has a great effect on the amount of liquid being atomized and the liquid "drainability" of the element during a short cycle injection as required when used with diesel injection valves, for example.
The present invention is based on such novel knowledge and relates to improvements on the ultrasonic injection nozzle of the type according to the invention of the aforesaid earlier patent application, and particularly to improvements on the vibrating element for use with such ultrasonic injection nozzle or ultrasonic atomizing apparatus, and is characterized by the configuration of the vibrating element.